It is a complicated question as to whether Atheism should be considered a religion, especially in certain contexts. But in some states atheists are banned from holding higher elected offices, and as far as I know, the Supreme Court has (passively) chosen to let that stand.
In the USA, religions that call their deity "God," perform Christian style prayer ceremonies and observe the Christmas holiday receive governmental recognition that other religions do not. Those religions are supported by slogans on currency, official prayer ceremonies in legislative assemblies, a phrase in the Pledge of Allegiance, a holiday, and tax payer funded Chaplins in many institutions including the military, public hospitals, and fire and police departments. (in some cases non-Judeo-Christian chaplins are also provided]
De Facto, the legal religious hierarchy in the USA is:
1. Christianity (privileges]
2. Judaism (support of their god and prayer rituals]
3. All other religions except Islam (tolerance]
4. Islam (some De Facto oppression]
5. Atheists/Agnostics etc. (some legal oppression]