Especially now it's important to provide citizenship documentation, passports or whatever is needed. Have it handy and ready to show. They're even strict at the Canadian boarder. They look carefully at everything. Found out how serious on a tour through certain parts of Alaska that crossed Canadian boarders. It took awhile for all of our tour group to be processed. They, the Boarder Guards, would not be rushed. Luckily we had been well prepared by Cruise Tour Director and everyone had proper documentation.
Had a wonderful time...but it would have been disterous if even one person had not had their 'papers' together.