Big Al:
American government is quite complicated in toto, but element by element it can be explained simply.
Each of the United 'States' is a complete self-governing body with its own written Constitution, a complete governmental system and legal system. Each of these states sends delegates to the Federal Government which has powers given it beyond State powers according to the U.S. Constitution, such as powers to wage war and control inter-State commerce.
Our U.S. House of Representatives is proportional representation, so that States with large populations have more votes than States with low populations. It is similar to the House of Commons. The Senate has two votes per State regardless of State size. It is like a House of Peers, only with power. A law can be initiated in either body but has to pass both bodies in similar language to go before the President, who can choose to sign it into law or veto it so it does not become law, or not sign it which means that after a set time it does not become law (pocket veto). Congress can over-ride a veto with a 3/4 majority in both the House and Senate. The House has primary power of the purse.
The House and the Senate have feelings of rivalry but a Representative (House) has common interests with the Senator from his or her State.
The Vice President of the United States is President of the Senate and has the power to decide a tie vote in the Senate (which happened Tuesday when Pence broke a tie to commence debate on the health care vote).
I'm sure this has kindled in you a newfound interest in the American system of Government.
("who just said bollocks?")