[Answer] Which Congressional Act gave Native Americans full U.S. citizenship?

Step 1 : Introduction to the question "Which Congressional Act gave Native Americans full U.S. citizenship?"

...In 1870, all U.S. citizens gained the right to vote, regardless of race, because of ratification of the 15th Amendment. However, Native Americans weren't allowed to enjoy these newly granted rights until the Snyder Act of 1924 granted full U.S. citizenship to those born in the U.S. Many in Congress and other government positions believed the Native Americans should more fully assimilate into American mainstream culture before they participated in voting. This brought on the devastating Dawes Act of 1887 that effectively dissolved Native tribes. Source: LOC.gov

[Ans] When did Congress grant citizenship to all Native Americans born in the United States?

Step 1 : Introduction to the question "When did Congress grant citizenship to all Native Americans born in the United States?"

...Do Native Americans have to pay taxes? Yes. They pay the same taxes as other citizens with the following exceptions: Federal income taxes are not levied on income from trust lands held for them by the U.S. State income taxes are not paid on income earned on a federal Indian reservation. Frequently Asked Questions | Indian Affairs 

Can a Native American become president of the United States? In this century, American Indian and Alaska Native men and women have held elected and appointed offices at all levels of state, local, and federal government. Charles Curtis, a member of the Kaw Tribe of Kansas, served as Vice President of the United States under President Herbert Hoover