US citizens CAN own land in Mexico. I have provided a source to prove my assertion and you have done nothing but restate your unsupported claim. Here, I will help you get started with the research...
https://www.google.com/webhp?source...ie=UTF-8#q=can+us+citizens+own+land+in+mexico
By the way, in 1995 (when Melania came here) there were modest barriers to US citizens owning property in Slovenia. Lots of countries/regions have these stupid laws.
The rest of your argument was unsupported speculation.
Many Mexicans will/would seek citizenship if there are legal opportunities. I know several that have. From what I have heard from the right, they are more opposed to immigrants gaining citizenship than a work visa, which makes your point seem strange.
You are the one that does not get it. The only difference between Melania and the immigrants Trumpettes attack is pigmentation.