Instead, we should have used a mix of intelligence operations, airstrikes, and diplomacy (from Clausewitz, the continuation of war by other means).
Osama Bin Laden was captured under the Obama Administration in Pakistan, not Afghanistan.
No WMD were ever found in Iraq.
The cost of both wars:
What could have been done with that:
So, all of the above could have been funded or fixed (~$6.44 Trillion) instead. For instance: Water Quality.
Apparently, the gleaming city of Dubai cost a little more than $300 Billion to build. So, we could have rebuilt all of America's major cities instead of funding those two wars.
We invaded both countries under the Bush Administration. So, most fault likely falls on the groups that coordinated with them to initiate those wars (along with that Administration itself.).
War's very bad and costly in the modern era. Wars don’t stimulate the overall economy (they do stimulate a few key defense industries but that’s it). Instead, wars tend to concentrate resources into wasteful projects with little lasting value. A lethal airstrike using a hellfire missile costs upwards of $150,000. Best case: terrorists are killed preventing destruction, death, and economic cost exceeding $150,000. Worser case: we just misfired and spent over $100K on something with no long-term economic value. Worst cast: we just killed innocent civilians.
If you have to [must, with absolute necessity] fight a war: use airstrikes (and hopefully non-lethal ones once such technologies become more prevalent) over ground operations, intelligence, and more clever diplomacy from the get-go. Diplomacy here does not mean talking things out to resolve differences. Rather, a mix of sanctions (almost always more effective than costly occupations), cautious drone strikes (with the permission of other sovereign partners), and so on. Above all else, avoid military occupations of foreign lands.
We should oppose authoritarian leaders and stand up for global justice but need to be more clever in how we do so. You can’t save the world if you can’t save yourself. You can’t win a war through Pyrrhic Victories.
Side-note: board games, war games, and such are fun but that’s where war should stay: in games. They teach people about conflict and demonstrate the cost and consequences of war. They inform and memorialize.
Domestic infrastructure building is almost always a better priority than costly foreign wars. Look at the most successful countries today (by almost any metric: HDI, GDP/Capita, etc.):