Well you see, the cost of government isn't proportional to GDP. It's all about gross dollars per citizen and %s how that tax burden will fall. Right now the marginal tax for those top income earners pay is 26-37%. You're suggesting we should try to push that up, yes? That number restricts income mobility into these outliers, less income is less wealth accumlation, pushing more people into the middle this can be seen in case after case. So I hope we agree there, yes?
Those high end income outliers even at lower % pay a lot of the gross. If those reduce the burden shifts more onto the middle/lower end, which requires higher tax rates as they have less income. For example in 2018, fed, state and local spend ~7.12 Trillion or $55,805 / household. The majority households could not afford their public share hence progressive taxation[a luxury of healthy top end income mobility with a healthy middle].
Median being in 2017: $61,372 per household $31,786 per capita. That puts the top end of the middle class at $122,744. You must get the current rate would have to raise if you reduce those at the top to a range of $47,372-$122,744. Which is even more distorted when you take into account these are gross income dollars not net and not taking into account demographic factos.
Maybe you think, the same amount of income would come in absent the top end. That though is a proven falsehood. Foreign capital enters via the 0.1% as they have investment capacity to be overseas and patriate that income.As to your chart which suggests Sweden has a less healthy middle class than Brazil or Mexico. It is obviously is too superficial to be meaningful.
What do I mean?
Let's look, how demographics compare between a $200,000+ income household to a $20,000-$25,000 household, shall we:
$200,000+: 6% rural, 51% from lower cost living areas(south/midwest); 6% single person households; 14% seniors. Two earners+: 77%. Work full-time: 80%. University educated: 76%.
$20,000-25,000: 17% rural, 64% from lower cost living area(south/midwest); 49% single households, 40% seniors. Two earners: 8%. Work full-time: 31%. University educated: 17%.
You just not comparing apples to apples here assuming that those in $20,000-25,000 are going to be magically transported to higher brackets if you higher the taxation at the top to the point of being punative to incme mobility about 300% of the mean [hughy long rule].