Take this with a grain of salt, considering the actions of the current administration...

But the US Constitution doesn't make that many distinctions between citizens and non-citizens, especially in the bill of rights, where most individual protections are laid out. The 4th amendment protects you from unwarranted search and seizure, and makes no restrictions based on nationality. The 5th amendment protects you from testifying against yourself. The 1st amendment protects your speech, the government can not suppress your opinions, and equally, they cannot compell you to make statements.

There are some "exceptions" to the 4th amendment, but those specifically have to do with protecting the borders and inspecting imports and exports. IMHO, those exceptions should be unconstitutional, but I'm not a bought and paid for SC justice, so fuck my opinion.

It's valid for anyone visiting the US. Even if they do so illegally. Its a right given by the constitution and its amendments and those apply to everyone in the US. Importantly, people often forget that the Constitution isn't a limiting document for the people. It's a limiting document for the government.