最近几天，拜登政府面临着新的移民潮在西南边境，共和党议员再次警告说，国际恐怖分子正试图通过墨西哥潜入该国。但美国官员和专家表示，这种警告没有准确捕捉到国际恐怖分子通过美墨边境进入美国的可能性有多大。
“认为西南边境对恐怖分子开放的想法是可笑的，”国家边境局局长亚历克斯·诺拉斯特说移居卡托研究所的研究。"政府没有证据表明恐怖分子利用西南边境进入美国。"
加州众议院少数党领袖凯文·麦卡锡周一在访问得克萨斯州边境期间，在记者和摄像机前透露，边境巡逻人员刚刚告诉他，涉嫌恐怖分子最近在试图进入美国时被捕。
“你在他们眼里看到了，他们在名单上...“恐怖分子监视名单，”麦卡锡说。
“他们现在正在寻找来自也门、伊朗和土耳其的人，那些在恐怖分子监视名单上的人，”他补充说。
其他共和党人也提出了类似的警告。
纽约众议员约翰·卡特科(John Katko)在与麦卡锡(McCarthy)和其他十几个人举行的新闻发布会上说:“他们在恐怖主义监视名单上的个人现在开始利用南部边境。”
吉姆·沃森/法新社通过盖蒂图像，文件
国土安全部部长亚历杭德罗·马约尔卡斯在每日新闻发布会上发言
具体来说，据知情人士透露，1月28日，一名在新墨西哥边境被捕的塞尔维亚国民与美国政府恐怖分子筛查数据库(或TSDB)中的某人匹配。此外，该消息来源称，数据库中的另外三人都来自也门，最近在边境被抓获。
但是出现在恐怖监视名单上并不意味着某人一定是恐怖分子，边境巡逻人员或海关官员遇到的人出现在恐怖监视名单上的情况非常罕见。
一名国土安全部高级调查官员在2018年告诉国会，“不到0.0001%的(海关和边境保护局)不可接受的遭遇和担忧涉及被列入恐怖分子筛查数据库(TSDB)的人”。
唐纳德·特朗普(Donald Trump)总统领导下的国土安全部发言人大卫·拉潘(David Lapan)在谈到观察名单时说:“这是一个警告，并不意味着你在现场逮捕了那个人并对他们提出指控。”“人们以多种不同的方式登上恐怖观察名单。有时候是认错人了。”
一位不愿透露姓名的美国官员指出，其他人最终出现在观察名单上，只是因为他们是一名已知恐怖分子的“表弟、朋友或清洁工”。
此外，美国国土安全部部长亚历杭德罗·马约尔卡斯(Alejandro Mayorkas)在周三的众议院听证会上向议员们建议，美国政府已经建立了防止恐怖分子进入该国的系统，最近几个月成功拦截了政府监视名单上的四人就是证明。
马约尔卡斯说，试图潜入美国的恐怖分子“不是一个新现象”，但“正是因为我们自国土安全部成立以来建立的多层安全机构[和]架构，我们事实上能够识别和逮捕他们”。“我们实际上是根据我们的情报和审查程序拒绝他们入境的，这些程序在过去几年里变得越来越复杂。”
保罗·拉杰/路透社
众议院少数党领袖凯文·麦卡锡在一个共和党代表团参观期间向媒体发表讲话
至于卡托研究所移民研究主任诺拉斯特，他在一份关于1975年至2017年间美国外国出生的恐怖分子风险的报告中研究了这个问题。在那段时间里，3100多万非法入境者中有9人成为了恐怖分子——其中包括3名在美国长大的马其顿兄弟，他们在孩童时期就进入了这个国家。
拉潘告诉美国广播公司新闻，提到9.11劫机者，他们都是乘飞机进入美国的，签证过期了。
“这并不是说发生的可能性为零，但我们从未见过这是一个重大风险的证据，”他说。
这位美国官员补充说，事实上，“美国从未发生过非法越过南部边境的恐怖袭击”。
Making sense of GOP claims about who is crossing the border
In recent days, as the Biden administration faces anew surge of migrantsalong the southwest border, Republican lawmakers are renewing warnings that international terrorists are trying to slip into the country through Mexico. But U.S. officials and experts say such warnings don't accurately capture how unlikely it is that international terrorists could access the United States through the U.S.-Mexico border.
"The notion that the Southwest border is open to terrorists is ludicrous," said Alex Nowrasteh, the director ofimmigrationstudies at the Cato Institute. "The government has shown no evidence that terrorists use the Southwest border to get into the United States."
Speaking before reporters and cameras during a visit to the border in Texas on Monday, House Minority Leader Kevin McCarthy, R-Calif., disclosed that border patrol agents had just told him that suspected terrorists were recently apprehended trying to enter the United States.
"You saw in their eyes, they're on the list ... the terrorist watch list," McCarthy said.
"They are now finding people from Yemen and Iran and Turkey, people on the terrorist watch list," he added.
Other Republicans offered similar warnings.
"Individuals that they have on the watchlist for terrorism are now starting to exploit the southern border," Rep. John Katko, R-N.Y., said at the news conference with McCarthy and a dozen others.
Specifically, on Jan. 28, a Serbian national apprehended at the border in New Mexico was a positive match for someone on the U.S. government's Terrorist Screening Database, or TSDB, according to a source familiar with the matter. In addition, three others on the database -- all from Yemen -- were recently caught at the border, the source said.
But showing up on a terror watchlist doesn't mean someone is necessarily a terrorist, and it's exceedingly rare for someone encountered by a Border Patrol agent or a customs officer to be on that terrorist watchlist.
"Less than 0.0001 percent of total [Customs and Border Protection] inadmissible encounters and apprehensions involve persons who are watchlisted on the Terrorist Screening Database (TSDB)," a senior Homeland Security Investigations official told Congress in 2018.
"It's an alert, it doesn't mean you arrest that person on site and charge them," David Lapan, a spokesman for the Department of Homeland Security under President Donald Trump, said of the watchlist. "There are many different ways that people end up on the terror watchlist. Sometimes it's a mistaken identity."
Others end up on the watchlist simply because they are "a cousin or a friend or a house cleaner" to a known terrorist, one U.S. official, speaking on the condition of anonymity, noted.
Furthermore, the U.S. government has established systems to prevent terrorists from entering the country -- as exhibited by the fact that four people on the government watchlist were successfully intercepted in recent months, Homeland Security Secretary Alejandro Mayorkas suggested to lawmakers during a House hearing on Wednesday.
Terrorists trying to sneak into the United States is "not a new phenomenon," but "it is because of our multi-layered security apparatus [and] architecture that we have built since the commencement of the Department of Homeland Security that we are in fact able to identify and apprehend them," Mayorkas said. "We actually deny them entry based on our intelligence and based on our vetting procedures, which have only grown in sophistication over the years."
As for Nowrasteh, the director of immigration studies at the Cato Institute, he studied the topic in a report on the risk of foreign-born terrorists in the U.S. between 1975 and 2017. In that time period, nine illegal immigrants of the more than 31 million people who entered the country illegally became terrorists – including three Macedonian brothers who entered the country as children and were raised in the United States.
"There are more people in the country illegally that overstay their visas than come across the southwest border," Lapan told ABC News, referencing the 9/11 hijackers, who all entered the United States on airplanes and overstayed their visas.
"It's not that there's zero chance of that happening, but we've just never seen evidence that it's a significant risk," he said.
In fact, "There has never been a terrorist attack in the United States by someone who illegally crossed the southern border," the U.S. official added.
