I flew Mexico City-SLC this month and there was no security beyond customs and immigration. My memory of IAH last year from Mexico City is that full TSA screen

I flew Mexico City-SLC this month and there was no security beyond customs and immigration. My memory of IAH last year from Mexico City is that full TSA screening was required, but that was before backscatter machines. One more data point. These may be useful for someone looking to enter the USA on a direct flight.