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I can't comment on the specifics of American elections and how different wins have been interpreted but at a more abstract level, things are actually the other way around: the United States is notable historically for the fact that presidential candidates tend to, on average, win by *bigger* margins than in many western democratic nations. This table starts with the 2000 Presidential election in the US, and then counts back up to 10 elections (Presidential for the US and France; parliamentary for all others), which in most cases takes a country back to about the 1960s, tracking the difference in vote share between the party/candidate that came first and the party/candidate that came second (a minus indicates the party that came first was beaten in a majoritarian system by the party that came second, like Trump beat Clinton in '16):
| No. | USA | UK | Canada | France | Germany | Australia | New Zealand | Jamaica |
|---|---|---|---|---|---|---|---|---|
| 1 | -0.5 | 12.5 | 19.1 | 5.2 | 5.8 | -2 | 8.2 | 17.3 |
| 2 | 8.5 | 7.5 | 22.6 | 8 | 5 | 5 | 5.7 | 20 |
| 3 | 5.6 | 11.4 | 11.1 | 3.6 | 10.3 | 10.3 | 0.4 | 13.3 |
| 4 | 7.8 | 14.8 | 22.0 | 1.6 | 7.2 | 7.2 | 12.6 | 17.8 |
| 5 | 18.2 | 7 | 11.8 | 16.4 | 10.6 | 10.6 | 4 | 13.5 |
| 6 | 8.7 | 3.4 | -4.2 | 10.4 | 1.6 | 1.6 | 7 | 13 |
| 7 | 2.1 | -0.7 | 7.7 | 6 | 6 | -0.2 | 1.6 | |
| 8 | 23.2 | 3.3 | 3.4 | 0.9 | 0.9 | -0.6 | 1.4 | |
| 9 | 0.7 | 6.1 | 13.9 | 3.4 | 3.4 | 8 | 10.5 | |
| 10 | 22.6 | 0.7 | 7.8 | 8.3 | 8.3 | 6.9 | 11.5 | |
| Avg. | 9.7 | 6.6 | 11.5 | 7.5 | 5.9 | 5.9 | 4.6 | 12.2 |
So actually, the United States isn't all that remarkable in the history of western democracy - of these eight comparative countries, only Canada and Jamaica have a higher than average victory margin in major national elections, and Canada's would be lower if not for the fact the 1993 and 1997 elections were fought in the context of a collapse in one of the two major political parties that had been operating up until that point, fragmenting the opposition vote. Australia is the most useful comparison perhaps because the Australian authorities undertake what is called a Two Party Preferred count, where regardless of the result in each part of the country, each ballot (where voters have to rank all candidates in order of preference) is recounted to determine whether voters on the whole preferred the Labor Party or Liberal/National Coalition to win the election. On average, voters only favour one party by a margin of just shy of 53% - 47%. Likewise in France, where voters pick between the top two candidates in a run-off, the average margin of victory has varied wildly and averages out at under 10 points.
It is the effect of different voting systems that exaggerates or diminishes the public, political and media perception of how strong a win is. In a country like Germany, whilst a ten point lead is a strong result and an historic over-performance, the proportional system means it does not guarantee getting into government with a strong majority, as a leading party has only won more than half the seats in the Bundestag once since WWII, and so a party's ability to govern decisively is also determined by the balance of votes for other parties. But in a majoritarian system where votes are translated into seats in a way that tends to exaggerate the win of the victorious party or candidate, our sense of what constitutes a landslide can become warped.
In the case of the United States, the Electoral College means that in most elections a substantial share of the popular vote will be converted into a much bigger share of electoral votes, because a candidate who wins a state (with a couple of exceptions) will carry all of its electoral votes, and there is no requirement for the allocation of electoral votes to match the overall national vote - there are really ~50 separate elections happening for President, not one single election.
For example in 1988, George H W Bush beat Michael Dukakis by a margin of 7.8pts, 53.4% to 45.6%. This translated into an electoral vote margin of 426 - 112, or a 79.2% - 20.8% victory. Bush's practical margin for determining who wins power was 58.4pts. The Electoral College exaggerated the scale of Bush's win compared to the popular vote by a factor almost 8 times. But the same system could have just as easily cost Bush the Presidency if voters behaved slightly differently in 12 key states.