The survival of John I and the fact he would leave male heirs would definitely prevent the Hundread Years' War. With a surviving John I, there would be no need to determine who would be the next ruler of France between John I's half sister Joan of Navarra and his uncle Philip of Poitiers (later Philip V OTL). Thus, the question of Salic Law never arises and it will never be needed to know if boys born from female lines can take the French crown (case of Edward III).
No Hundread Years' War probably has huge consequence on French and English History. Conflicts could still arise though as Gascony is still in English hands, making the English King a French Vassal as Duke of Aquitaine. And the French will probably want to annex Gascony...
Regarding John I's reign, it will begin with 14 years of Regency from 1316 to 1330. People who are likely to play a huge role during that period are :
1) Philip of Poitiers - Brother of Louis X and Uncle of John I. OTL Philip V of France who died in 1322. The most politically able of the three sons of Philip IV the Fair and the one already in charge during the pregnancy of Clementia of Hungary.
2) Charles of La Marche - Youngest Brother of Louis X and Uncle of John I. OTL Charles IV of France who died in 1328. Not really important, but he would probably play some sort of role.
3) Charles of Valois - Brother of Philip IV. The most powerful baron of France in 1316. Died 1325 OTL. Very conservative, but Philip of Poitiers was able to neutralize him.
4) Philip of Valois - Son of the previous and OTL Philip VI of France. A great Knight, but nothing more.
5) Clementia of Hungary - Louis X's widow, and thus John I's mother. Probably won't have any political power, but probably she will probably influence her son's character. She was said to be very pious.
John I would probably live for 50-60 years, making him die between 1366 and 1376. He would reign as King of France and Navarre, since there would be no need to separate the two crowns.
As King of France, John I will probably play some sort of role in the Papal crisis. His grandfather, Philip IV, played a part in having the Pope moving to Avignon. Question is : would John I wish for the Papacy to return to Rome?
Another matter will be the Burgundian succession, unless the POD butterflied away. Duke Philip I (1346-1361) died childless : his heir would be John I's nephew, OTL Charles II of Navarra, according to primogeniture law. But OTL, the succession went to OTL John II of France by proximity of blood. Maybe John I will want his nephew rather than his cousin to get the crown...
In a previous thread I started on the same subject, I asked for John I's potential wives. He could be married starting from 1330 as he would be 14.
Here are the names that were given to me :
Constance of Aragon (1318-1346) - daughter of Alphonso IV of Aragon. OTL, she married James III of Majorca in 1336.
Eleanor of Woodtsock (1318-1355) - daughter of Edward II of England and Isabella of France, making her a First cousin of John I. She married Reginald II of Guelders "the Balck" OTL in 1332.
Elisabeth of Sicily (1310-1349) - daughter of Frederick III of Sicily. Married Stephen II of Bavaria in 1328 OTL.
Margaret of Bohemia (1313-1341) - daughter of John of Bohemia. Married Henry XIV of Bavaria in 1328 OTL.
Bonne of Luxembourg (1315-1349) - daughter of John of Bohemia. Married John II of France OTL in 1332, John I's cousin.