What a shame for you that this thread is not about other religions, then.
I'm sorry; I asked for a source for your $3 billion USA-only number. This story only repeats the same $7 billion dollar number that we both know, but specifies that it is for the entire religion, not just the USA (15 million people):
Nielsen’s complaint comes as many Mormons across the United States are engaged in discussions with their bishops, traditionally held in December, to “settle” their dues to the church. His estimate of $7 billion in annual revenue points to a relatively high rate of contributions from the 15 million members.
So I'm going to have to ask you again: What is your source for $3 billion in tithes from US members
only?
That's what you claimed, and I'm going to assume that this claim was actually based on something in the real world. Come out with it, please.
It depends at what rate they were to give. A lot of churches don't believe in tithing to begin with, so at least some of what is found in that $44 billion figure is probably larger individual donations. But, for instance, if we take the numbers for Catholics in the USA from the WP article you yourself linked to, we have $8 billion received by the RCC in America in 2005, at a time when there were apparently 75 million Catholics in the USA. That gives them a per capita giving amount of $106.66, which if you break it down to weekly giving is about $2.05 per person -- surely because some give more than that and subsidize those who do not give (because they're babies, or too poor, or just don't want to, or whatever). I'm suggesting nothing more than this when I ask about the contributions of wealthy Mormons artificially inflating the total of Mormon giving, as the same would be true of literally any kind of religious group. There's always going to be some who give more and some who give less, and some who don't give at all. (At least not monetarily; there are certainly other ways to give, such as through volunteering.)