An unbiased perspective on the most probable outcome
Early 1920s: Austria struggles to hold together, but Central Europe does much better than OTL.
Late 1920s: Austria sees a significant degree of economic recovery, struggles to finance rebuilding of military.
Early 1930s: Depression makes reparation payments difficult, rebuilding of military halted.
Late 1930s: Economic recovery, WWI debts becoming less significant, military rebuilt. Mussolini invades Ethiopia and Albania. Austria is a difficult target so Hitler goes after Poland first. Poland is triple partitioned by Germany, Soviet Union, Austria along 1914 borders.
Germany invades Soviet Union with surprise attack in 1939 and takes Poland. After four years the Soviets push the Germans beyond to prewar borders, secure Baltics. Military coups Hitler. Austria offers to protect Germany in exchange for restoration of German monarchs and several Habsburg cadets to be able to marry Catholic states; German military complies. Soviet Union backs down to Austrian ultimatum, agrees to annex only Baltic. Secret agreement regarding Romania.
In 1944, Austria, Russia, and Bulgaria force Romania to return to 1914 borders without shot being fired.
Italy tries to exploit chaos in Europe with war against Greece. Bogged down in Greece and Ethiopia simultaneously leaves them vulnerable. France and Austria decide to launch a quick containment war, resulting in Italy quickly collapsing. Austria gets its frontiers and satellites of 1861 restored.
1940s: Austria sees strong economic and population growth, enlarges further.
1950s: Economic boom. Austria is the economic center of Europe. Franco tries to place a Habsburg on the throne; France feels threatened. A war is launched by France to prevent themselves from being surrounded. France is soundly defeated by Austria, Germany, and Spain. Spain accepts a Habsburg on the throne. France fights a civil war between different extremist groups after government js discredited, resulting in the French right winning and the Bourbons being restored. France loses its colonies.
1960s: Austria sponsors decolonization movements around the world, offering financial assistance. Colonies accept Habsburg monarchs to demonstrate they are civilized. Latin American dictatorships accept Habsburg monarchs as well. Austria sends first man to the moon.
1970s: France and Italy both intermarry with Habsburg royal family, colonial era is effectively over internationally. Congo, Angola, and most Catholic leaning African states accept Habsburgs.
1980s: Austria invents the internet as we know it today.
1990s: Former Eastern Bloc accept Habsburg monarchs to get access to easy finance and technology, not appear backwards.
2000s: Habsburgs build first underwater city. Emperor Otto von Habsburg, on a stroll in the University of Vienna, notices flaw in physics department. Discovers fusion.
2010s: Austria builds first city on the moon, send first man to Mars.
2020s: Karl von Habsburg discovers cure for COVID. Despite underfunding from Hungarians, Austria makes first contact with advanced aliens. Space conquistadors introduce diseases, wipe out alien civilization, begin converting it to Catholicism and place Habsburg institutions on top of native institutions.