> costs ~$15 for the same in the United States
I'm not sure where you get $15. The linked site says $8:
"with 1GB costing an average $12.55 in Canada and $8.00 in the US."
Nor do I get why you think all of Asia is inexpensive. South Korea is far worse than the US, despite a far lower median income, at $10.94 average. If you adjust that to the US, it's more like $24 (200% higher than the US). And Japan is fairly bad vs global prices as well when adjusted for income levels (around $6 to $6.50 equivalent in US terms).
Why are US prices higher than they should be? Two primary reasons. First, the two big telcos initiated (and held) the market at a very high price point from inception. The US was the first large cellular and smartphone market. It has taken limited competition, primarily in the form of T-Mobile, more than a decade to drag those high prices downward.
Second, wealth / income adjustments. Consider the Ukraine example. The US has ~20 times the GDP per capita of Ukraine in a typical year. Their $0.46 cost is comparable to more like $9.20 with a US adjustment, which is higher than the US cost. US median disposable incomes are among the highest, only comparable to smaller affluent countries like Australia, Sweden, Norway, Denmark and Switzerland.
You also can't sell 1gb for $10 in Ukraine, it's not a very good business model. The people can't afford those prices. The telecom operators in countries like Ukraine do not make very much money selling mobile plans.
Most telecom operators around the world operate at very thin margins with low profits. Verizon by itself generated $30.4 billion in operating income in 2019. AT&T generated $29.4 billion in operating income. T-Mobile generated $5.7 billion in operating income.
So between the three US telecom operators, that's $65.6 billion in operating income every year (best compared to Apple or Microsoft in size). The entire rest of the world has nothing remotely like that profit bonanza, outside of a select few large operators.